Cutting mechanism for sewing machines



Feb. 20, 1968 P. E. BURTON CUTTING MECHANISM FOR SEWING MACHINES FiledJan. 5, 1966 INVENTO/Q Arrow 5y ite States Patet Gfiice 3,369,599Patented Feb. 20, 1968 3,369,509 CUTTING MECHANISM FOR SEWING MACHINESPerry E. Burton, Duluth, Ga, assignor to Sunbrand Corporation, Chamblee,Ga., a corporation of Georgia Filed Jan. 3, 1966, Ser. No. 518,164 8Claims. (Cl. 112129) This invention relates to cutting mechanisms, andmore particularly, to an improved cutting mechanism for use with asewing machine for cutting thread chains, braid, belting, or the likepassing through the sewing machine.

Prior art cutting mechanism of this general type have normally beenoperated with a scissor-like action, as suggested by US. Patent No.1,286,113, issued Nov. 26, 1918 to A. S. Robinson, or with a guillotinecut-off mechanism such as that illustrated in Patent No. 3,146,742issued Sept. 1, 1964 to H. R. George et al. While these prior artdevices have been known and widely used commercially, they have not beenentirely satisfactory due, in part, to the relative complexity of theknown devices, and to the maintenance necessary to keep the shearingblades properly adjusted and sharpened. Accordingly, the primary objectof the present invention is to provide an improved cutting mechanism,hereinafter referred to as a chopper, for use with a sewing machine, andwhich employs the chopping action of a blade striking an anvil to affectthe cutting operation.

Another object is to provide an air actuated chopper for use withexisting sewing machines and which may be mounted on the sewing machinetable so that extensive modification of the machine is unnecessary.Another object is to provide an air actuated chopping mechanismemploying a torsion bar mounting to reduce operating stresses in thechopper.

Another object is to provide a fully suspended chopper which allowsfreedom of movement of material to the right and to the left of thecutting blade to the extent normally permitted by the sewing machineitself.

Another object is to provide an improved air cylinder for a chopperwhich cylinder includes an automatic valving system built into thecylinder itself, and resulting in tremendous impact of the cutting bladewith the material being operated upon or processed at the time.

Another object is to provide over-all simplicity in such a device.

Another objpect is to provide ease of maintenance and serving a textilechopper.

These and other objects made clear during the further progress of thisspecification are accomplished by means of the instant invention, a fulland complete understanding of which is facilitated by reference to thedrawing herein, in which:

FIG. 1 is a view in perspective, fragmentary in part, showing theinstant device mounted in operative position on a sewing machine;

FIG. 2 is a somewhat reduced end view of the structure of FIG. 1; and

FIG. 3 is a longitudinal sectional view of the air cylinder used todrive the knife blade herein against the striking plate in what might bedescribed as a pinching or die action.

Referring now to the drawings, in which identical numerals are used todescribe identical or similar elements throughout the various figuresthereof, indicates a fiat wooden table into which is recessed aconventional sewing machine 11; arm 12, and sewing head 13 beingintegral parts of said device. A mounting base 14 is provided withmounting screw holes 15 and 16, into which are aifixed suitable screwsto secure such firmly in place on the table 10. A cantilevered mounting17 rises from one end of said base as at 18 and extends first upwardly,then laterally and slightly to the rear of base 14 to position cuttingblade 19, its holding or mounting element 20, blade guard 21 and supercharged air cylinder 22 for operative engagement of blade 19 withstriker plate 23 mounted on 14 at the end thereof opposite end 18.

Plate 23 is formed of stainless steel, preferably Armco 17-4-P.H., whichis known as a self-hardening or precipitation hardening metal, workhardening severely under stress such as that generated by the instantchopper blade, which is precision ground chrome tungsten steel, with itsedge ground at a relatively steep angle in order to give it thenecessary strength and resistance to chipping.

Said striker plate is originally used in an annealed state, resulting ina soft surface for the blade to strike, which facilitates perfect matingof the blade edge with the plate. However, after repeated blows the areabeing impacted by the blade hardens, extending the service life of theapproximately one sixteenth of an inch thick plate by several hundredthousand cycles. This is a disadvantage in drawing and stampingoperations, but highly desirable in the case of the instant operation.

Since the blows of the blade on the striker plate result in a ratherhigh noise level, a padding of neoprene cork or the like 24 ispositioned under the plate.

Blade holder 20 is machined at a taper for the purpose of making thebottom very narrow so as not to interfere with the cutting operation,and has a ledge 26 against which the top edge of the blade rests to takethe strain of the cutting action away from the two small screws 27 whichthe holder is tapped to receive in securing the blade itself. Saidholder is drilled and tapped to screw on the end of the air cylinderpiston rod.

Said air cylinder 22 is of suitable bore and stroke, with its headmachined to provide a chamber 28 of suflicient size to receive aresilient female sealing member having a central aperture 29 the desiredsize; said seal being held in place by a resilient gasket ring 30. Thepiston 31 from the cylinder is drilled and tapped precisely in its topcenter 31A with a suitable thread and a male sealing member or stud 32afiixed thereto. The cylinder wall is drilled with a small hole 33 nearits top edge between female seal member and piston 31 when such is inretracted position; and the lower end block of the cylinder is drilledwith three small holes 34 to facilitate escape of air trapped below thepiston on the down-stroke. The operation of the piston and related partsis as follows: High pressure air from a remote source such as acompressor or tank (not shown) is introduced through line 35 into anadjustable power control unit 36 having a pressure guage 37, adjustableby element 38, the air then passing into the cylinder through surge tube39. At this point the male and female sealing members forming thepressure sensitive dump valve are held together in their sealingposition by piston return spring 40. Air pressure builds up withinchamber 28 to a point high enough to push the male sealing member fromits seat against the pressure of spring 40. The pressure required tocompress spring 40 by pressing against a relatively small area of themale seal is substantially greater than that required to compress thespring when the entire end area of piston 31 is subjected to pressure.Thus relatively high pressure is permitted to build up within chamber 28and tube 39 before piston 31 begins to move. When the male seal 32leaves the female seal 29, the high pressure air from chamber 28 isdumped onto the relative large end area of the already moving piston,causing it the accelerate rapidly. When the rapidly descending piston 31and the pinching or chopping blade 19 are stopped against the surface ofstriking plate, or anvil 23, the impact is effective to cut or chop anytextile or the like material positioned on the anvil.

A suitable manually operable control valve, which may be foot or kneeoperated, is provided to control the flow of pressurized air to cylinder22.. The valve is operated as soon as piston 31 is driven downward tocut off the pressurized air to cylinder 22, thereby allowing thecylinder to exhaust through port 33 and valve 36, as the piston 31 isreturned to its retracted position under the force of spring 40. As themale sealing member enters the female seal, approximately threesixteenth of an inch of the return stroke remains. Air trapped betweenthe piston top and the female seal is compressed and escapes through thesmall hole 33 thereby allowing the piston to fully retract, after whichit is ready for another cutting or severing operation.

Cantilevered mounting arm 17 is provided with a laterally extendingbrace 17A provided with a brace screw 17B and associated nuts 17C, whichscrew is extended upwardly in mounting to fit snugly against theunderside of arm 12, which means that while there is no drilling of themachine at this point, what amounts to three-point suspension is nowestablished in conjunction with screws passed through holes 15 and 16and into table 10.

The importance of this becomes apparent when considered in conjunctionwith the fact that in order to obtain rigidity in the power ranges inwhich the instant chopper operates, it is necessary to disperse theforces generated, over several points. The power used if attacheddirectly to the sewing machine head 13 would force the chopper directlyaway from its base. In order to avoid this, the tubular suspendedmounting member 17 was bent slightly rearwardly and the brace screw 178provided. In operation, when the power cylinder drives the cutting bladeagainst the striker plate 23, the reaction force on the cylinder causesthe brace and screw to contact the sewing machine underarm with greaterforce than normally. The longitudinal axis of cylinder 22 is inclinedrcarwardly slightly, as seen in FIG. 2, so that the line of action ofthe reaction force passes rearwardly of the point of contact of screw1713 with machine arm 12. This arrangement converts much of the force ofthe cutting impact into a twisting motion, allowing the tubular memberto act as a torsion bar and absorb the greater portion of the force, theremainder being expended on the underarm of the sewing machine, and thetwo screws holding the flat base 14 to table it) with subsequentdistribution.

Blade guard element 21 is constructed so as to be adjustable upwardly ordownwardly to allow free adjustment or passage of the item to be cut,yet at the same time prevent accidental insertion of a finger or fingersbeneath the cutting blade. Said guard is fabricated of high carbonsteel, hardened to a point where it will break before bending andthereby preventing changes by a user, the guard serving as a blade guidealso. It is contoured in such a manner that the two screws which hold onthe blade are in constant contact with it during the downward stroke ofair cylinder and blade. If the guard is removed or designed in anymanner other than specified, the chopper will, not operate as a cutterbecause of radial movement of the blade because the cutting unit ismounted at an angle,.and such movement results in only one corner of theblade striking the cutting surface.

From the foregoing it is believed that the operation of the instant airchopper will be obvious; and further that it and particularly the veryhigh impact air cylinder taught herein is adapted to many uses andapplications additional to those specifically described herein.

While there has been shown and described in considerable detail hereinone form of the instant device, it is apparent that no limitation isintended or implied thereby, but on the contrary, various modifications,additions,

4 deletions, reconstructions and the like may be resorted to withoutdeparting from the basic invention and appended claims, which are to beaccorded a scopeand interpretation fairly in keeping with thecontribution to the art.

I claim:

1. A cutting mechanism for use with a sewing machine having anoverhanging arm comprising, a frame, means mounting said frame on asupporting surface, an anvil having a generally horizontal surfaceadjacent to the stitch forming mechanism of the sewing machine, achopping blade mounted on said frame for reciprocal movement between acutting position in engagement with said hori zontal surface, and aretracted position spaced above said surface, means for forcefullydriving said blade from said retracted position into impact with saidanvil at said cutting position to cut material positioned on saidhorizontal surface by a pinching action, said frame including acantilevered arm extending generally longitudinally of and in olfsetrelation to said overhanging arm, means mounting said blade drivingmeans on the free end of said cantilevered arm and means fixed to saidcantilevered arm intermediate the ends thereof engaging said overhangingarm thereby producing a torsional stress on said cantilevered arm uponimpact of said blade with said anvil.

2. The'cutting mechanism defined in claim 1 further including meansresiliently urging said blade into retracted position.

3. The device of claim 1, in which the cantilevered arm is tubular inform and provided with a brace and brace screw for contacting theoverhanging arm of the sewing machine, thereby setting up said torsionbar action when the cutter mechanism is operated.

4. The device of claim 1, in which means are provided to regulate theamount of air entering the cylinder at a given time and under givenworking conditions.

5. The device of claim 1, in which a shock absorbing element is providedbeneath the anvil, thereby reducing both noise and vibration when saidcutting mechanism is functioning.

6. The cutting mechanism in claim 1 wherein said means for driving saidblade comprises a quick acting pneumatic cylinder mounted on said frame.

7. The device of claim 6, in which the pneumatic cylinder is providedwith a male and a female sealing element, a spring holding the piston innormally retracted position until such time as such spring is overcomeby air pressure causing the seals to unseat and drive the pistondownwardly with tremendous impact of the pinching-cutting blade againstthe striker plate to sever an object posi' tioned thereon.

8. The device of claim 7, in which the pneumatic cylinder is vented bothabove and below its piston to facilitate discharge of surplus air bothon the downward and upward movement of the piston while in operation.

References Cited UNITED STATES PATENTS 3,063,321 11/1962 Nicolay 112-129XR 3,238,850 I 3/1966 Desmarchelier 91--394 3,250,237 5/1966 Myska112252 3,260,167 7/1966 Pedersen et al. 91-396 3,320,926 5/1967 Dexteret al. 83-658 FOREIGN PATENTS 1,157,897 11/1963 Germany.

JORDAN FRANKLIN, Primary Examiner,

H. H. HUNTER, Examiner.

1. A CUTTING MECHANISM FOR USE WITH A SEWING MACHINE HAVING ANOVERHANGING ARM COMPRISING, A FRAME, MEANS MOUNTING SAID FRAME ON ASUPPORTING SURFACE, AN ANVIL HAVING A GENERALLY HORIZONTAL SURFACEADJACENT TO THE STITCH FORMING MECHANISM OF THE SEWING MACHINE, ACHOPPING BLADE MOUNTEED ON SAID FRAME FOR RECIPROCAL MOVEMENT BETWEEN ACUTTING POSITION IN ENGAGEMENT WITH SAID HORIZONTAL SURFACE AND ARETRACTED POSITION SPACED ABOVE SAID SURFACE, MEANS FOR FORCEFULLYDRIVING SAID BLADE FROM SAID RETRACTED POSITION INTO IMPACT WITH SAIDANVIL AT SAID CUTTING POSITION TO CUT MATERIAL POSITIONED ON SAIDHORIZONTAL SURFACE BY A PINCHING ACTION, SAID FRAME INCLUDING ACANTILEVERED ARM EXTENDING GENERALLY LONGITUDINALLY OF